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ABSTRACT Achieving high‐quality perovskite (ABX 3 ) film is the key to the improvement of efficiency and stability of perovskite solar cells (PSCs) for subsequent commercialization, yet traditional crystallization relying on the quick reaction between AX and BX 2 components often involves photoinactive intermediate phases and imperfections that go against the device performance. Herein, we report a new strategy for retarding perovskite crystallization and defect passivation by customizing the non‐skeletal groups (such as ‐F, ‐H, ‐OC 2 H 5 and etc.) in covalent organic frameworks (COFs). Given the discernable charge transfer feature depending on donor‐acceptor interaction strength, theoretical and experimental results demonstrate that, compared to the electron‐donating group, the electron‐withdrawing ‐F atoms induce local asymmetric electron distribution, forming a negative Lewis‐base center at acceptor unit, a positive π‐acidic center at donor unit, and a hydrogen bond center at side chain to discretely interact with PbI 2 , free I − anions and organic cations (formamidinium, FA + ). As a result, the F‐functionalized‐COFs enable micro‐spatial all‐components‐delocalized crystallization and defect passivation, thus promoting the efficiency of inverted PSC up to 26.02%, along with the significantly improved stability after aging under 75°C for 1000 h, 10% relative humidity for 2000 h, and continuous illumination over 1100 h.
Zhang et al. (Tue,) studied this question.